In some integrated circuit packaging, underfill material is used to fill the space between a chip and a substrate on which the chip is mounted with solder bumps. The underfill protects the solder bumps from moisture or other environmental hazards, and provides additional mechanical strength to the assembly as well as compensates for any thermal expansion difference between the chip and the substrate. However, the underfill material can overflow outside the intended area and the spillover can contaminate the package on package (PoP) pad for solder bumps on the substrate. Some packages use damming material outside the underfill to block the overflow, which incurs additional cost and less accuracy of width/height control due to soft liquid damming material and tool tolerance.